DC-DC converters installed in vehicles, such as the one disclosed in Japanese Patent No. 3544307, has been known. This DC-DC converter accommodates within its case a transformer, switching elements connected to the primary coil of the transformer for switching the flow of electrical current to the primary coil, and rectifying elements connected to the secondary coil of the transformer.
Due to the enlargement of the cabin space and the higher performance of vehicles in recent years, the space for mounting DC-DC converters is increasingly limited. This calls for further miniaturization of DC-DC converters. If the DC-DC converter is miniaturized, the electronic components (the transformer, the switching elements, the rectifying elements, etc.) become more densely populated in the case. The heat generated by these and adjacent electronic components may potentially raise the temperatures of the electronic components above their heat-resistant limits. This can cause a problem particularly if the switching elements and the rectifying elements, which have relatively low heat-resistant temperatures, and the transformer, which has a relatively high heat-resistant temperature, are arranged close to one another in the case.
To address this issue, a metal heat sink may be mounted on the substrate to which the electronic components, such as the switching elements and the rectifying elements, are connected in order to cool the interior of the case. This was expected to protect the electronic components with relatively low heat-resistant temperatures. Such technology is known from Japanese Patent No. 3641603.